Near pure surface uplift of the Argentine Frontal Cordillera: insights from (U–Th)/He thermochronometry and geomorphic analysis
Near pure surface uplift of the Argentine Frontal Cordillera: insights from (U–Th)/He thermochronometry and geomorphic analysis
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阿根廷额科迪勒拉山脉近乎纯粹的地表隆起：(U-Th)/He 测温法和地貌分析的见解
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发表时间：
2014
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通讯作者：
J. Metcalf
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作者：
G. Hoke;N. Graber;J. Mescua;L. Giambiagi;P. Fitzgerald;J. Metcalf
摘要/ Abstract摘要：本文利用深切河谷古地表边界垂直样带的磷灰石(U-Th)/He热年代学资料和地貌分析资料，研究了32°~ 34°南纬范围内安第斯山脉前陆近端隆升的时间及其演化关系。磷灰石(U-Th)/He （AHe）分析结果复杂。然而，数据显示出正的年龄-海拔变化趋势，高海拔的样本比低海拔的样本产生更大的AHe年龄。两个剖面的断坡发生在摄氏25 Ma，将非常缓慢的冷却和或停留在部分保留区（摄氏10 m/Myr的坡度）与摄氏60-100 m/Myr的较低海拔的冷却速率分开。较早的AHe年龄表明：(1)额科迪勒拉的最小埋藏和/或(2)中新世前中期显著的局部浮雕。对相邻的向东排水的Río门多萨流域和Río Tunuyán流域的地貌分析显示，在海拔3000米以上的地区，景观上有冰川的印记，包括在冰川侵蚀期间形成的更大的陡度和更低的凹形。对顶壁高度的详细分析提供了沿整个前科迪勒拉东部侧翼和板块倾斜过渡以南的主科迪勒拉东部侧翼正在进行的岩石隆起的证据。
Abstract Apatite (U–Th)/He thermochronology from palaeosurface-bounded vertical transects collected in deeply incised river valleys with >2 km of relief, as well as geomorphic analysis, are used to examine the timing of uplift of the Frontal Cordillera and its relation to the evolution of the proximal portions of the Andean foreland between 32° and 34°S latitude. The results of apatite (U–Th)/He (AHe) analyses are complex. However, the data show positive age-elevation trends, with higher elevation samples yielding older AHe ages than samples at lower elevation. Slope breaks occur at c. 25 Ma in both profiles, separating very slow cooling and or residence within a partial retention zone (slope of c. 10 m/Myr) at the highest elevations from a slope of c. 60–100 m/Myr cooling rate at lower elevations. The older AHe ages suggest either (1) minimal burial of the Frontal Cordillera and/or (2) significant pre–middle Miocene local relief. Geomorphic analysis of the adjacent, east-draining Río Mendoza and Río Tunuyán catchments reveals a glacial imprint to the landscape at elevations above 3000 m, including greater channel steepness and lower profile concavities developed during glacial erosion. Detailed analysis of headwall heights provides evidence of ongoing rock uplift along the entire eastern flank of the Frontal Cordillera and in the eastern flank of the Principal Cordillera south of the slab dip transition.